The present invention relates to a suspension system for a vehicle and to a method of operation thereof, and more particularly relates to an active such suspension system for a vehicle and a method of operation thereof which provide particularly good inhibition of vertical oscillations of the body of the vehicle.
The present invention has been described in Japanese Patent Application Ser. No. Showa 61-180942 (1986), which was filed by an applicant the same as the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the text of said Japanese Patent Application and the claims and the drawings thereof; a copy is appended to the present application.
Various types of suspension for a vehicle have been utilized in the past. Particularly, so called active type suspensions have per se been conceived of. Particularly, in the article "Suspension Without Springs" published in the British magazine "Motor" on Sept. 10, 1983, in the article "On Active Service" published in the British magazine "Autocar" on the same date of Sept. 10, 1983, and in Japanese Patent Publication Ser. No. Showa 60-500662 (1985), there was proposed a vehicle suspension system not incorporating springs but instead suspending each of the wheels of the vehicle from the vehicle body by the use of an electrical-hydraulic type of servo actuator which produced a support force for displacing said vehicle wheel downwards with respect to said vehicle body, said support force being controlled by a control device to be increased or decreased according to a signal from a movement detection means which was provided for detecting relative movement between said vehicle wheel and said vehicle body.
However, in such a system, when there is a relative movement between the vehicle wheel and the vehicle body caused by an irregularity in the surface of the road upon which said vehicle wheel is running, the actuator for this vehicle wheel produces a support force which corresponds to the amount of such relative movement, and as a result of this, when the vehicle incorporating this system is traveling over a road the surface of which is irregular, the support force with which the actuator supports the vehicle body over the vehicle wheels is increased and decreased, and this increasing and decreasing force is transmitted to the vehicle body, as a result of which the vehicle body oscillates upwards and downwards in the vertical direction, in substantially the same way as necessarily occurs with a conventional type of suspension incorporating springs. In other words, the suspensions described in the above publications, although they do incorporate active type servo actuators, in their operational characteristics behave like conventional suspensions which are equipped with springs and shock absorbers, and accordingly these suspensions do not prevent vertical oscillations of the body of the vehicle when the vehicle is traveling over a road the surface of which is irregular or the like, and thus the riding characteristics of the vehicle remain as leaving something to be desired.